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40mm vs 50mm FLE vs non FLE



I found nowhere on the net an explicit comparison between these 2 lenses in their different versions among each other.

Since 24mm is one of my favorite lenses in 135 for landscapes, I am thinking about buying something similar for Medium Format second hand. Unfortunately. There are different versions out there, which are according to MTF curves different in image quality.

1. Zeiss 4/40 non FLE
2. Zeiss 4/40 FLE
3. Zeiss 4/50 non FLE
4. Zeiss 4/40 FLE

My questions:

A. Since the image "impression" is different in 6x6 as in 135, I am not sure whether the mathematical equivalent to a 24mm in 135, the 40mm in MF would be the best choice. Any recommendation of your real life experience 40mm vs. 50 would be welcome.

B. The 40 and the 50 are second hand available in FLE and non FLE versions. I know that the FLE versions (FLE= floating elements) are better according to the MTF charts. (Has anybody MTF of the 4/40 non-FLE?) But how much do you really see the difference in real life situations between the FLE and non FLE versions? (prints maximum up to Din A3+)

C. If you see a difference between FLE and non FLE, is this difference only about sharpness/contrast or also in Colours, lens flare etc.?

Thanks in advance

Buen Amigo Dirk:
A)I have both 40 and 50mm CT* and in my Nikon f2 I like to use the old 20mm f/3.5... I like very very much the 40mm. I think that the 50mm is much like the 28mm in 135... 40mm seems to be a little bit mor than the 20mm in 135 (perhaps a 22mm).
B)I don't know the FLE, but I don't think that you coan see some difference in A3 size...
Un fuerte abrazo, que los Dioses te guíen.

Tito Chescotta
According to my experience, the FLE and the older versions perform on a similar level in the center of the image only, while at the edges and in the corners the FLE versions deliver considerably better image definition. As a rule of thumb: The FLE versions deliver 2x the resolving power off-center.
Does anyone have experience with the new 40MM IF? Is the distortion noticeable with architecture subjects?
"Double the resolving power off center" ????? That's a little hard to swallow. And it's not what the MTF curves tell me. Although I see you work with a 903 and 250 Super Achromat, indicating you know what "sharpness" is, on what do you base this conclusion ?

I believe you do not yet know dr. Kornelius J. Müller/Fleischer, so let me introduce him to you: he is a Zeiss Camera lens Divison employee.

I don't think you can't tell the resolution a lens is capable off from the MTF curves supplied by Zeiss, since what they do is contrast modulation at three set input frequencies, highest of which is a mere 40 line pairs per mm. Not quite near the claimed resolving power of 200 line pairs per mm, is it?

To judge resolution, you would need to gradually increase these input frequencies to find the one limiting frequency at which performance falls below acceptable levels.
Please, insert the word "show" between "what they do" and "is contrast modulation ..." in the second paragraph of my previous post.

My apologies!
I'm not even going to touch this one.
So, has everybody got their summer vacation plans made?
I'm going to sit up high in the Rockies in the US with an 8x10. Wonderful air up there !